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Draft — January 27 -5, 2005 <br />In the S -1 model, the LPT elevation is evaluated against the projected September 30 (end <br />of the water year) water surface elevation at Lake Powell. Releases are scheduled to be <br />the ROM release when Lake Powell is projected to end the year below the LPT elevation <br />(so long as Lake Mead remains above the WST elevation). When Lake Powell ends the <br />water year below the LPT elevation, releases the subsequent water year begin according <br />to the reduced monthly schedule as contained in the ROM monthly release schedule. <br />yam:• <br />The S -1 model imposes the transitory equalization level (TEL) at Lake Powell once <br />releases have been reduced to the ROM release. The TEL provides a method of creating <br />parity between the Upper and Lower Basins in the model, providing the Lower Basin a <br />method to recoup water without implementing a specific accounting scheme for payback. <br />ma,ekwaft -Aa ...: N" #"w Oft OwLPTdo"W 10 <br />Thus, the S -1 model will allow releases from Lake Powell to be reduced to the ROM <br />release when Lake Powell is below the LPT elevation of 3,560 feet (so long as Lake <br />Mead is above the WST elevation of 1,050 feet), but then as Lake Powell recovers, water <br />is shared with Lake Mead at a level less than the 602(a) Storage level. If there is at least <br />one year where the ROM release have been implemented in the model, equalization <br />releases subsequently take place at the TEL. The TEL is then used until active storage in <br />the Upper Basin exceeds 602(a) Storage on September 30, and Lakes Powell and Mead <br />are equalized under "normal operations." This could occur in one year of very good <br />hydrology, but will likely take more than one year in most model traces. <br />,• o Achieving <br />equalization of storage between Lakes Powell and Mead at the 602(a) Storage level <br />"wipes the slate clean." Only though a subsequent period of low inflow, with Lake <br />Powell again dropping below the LPT elevation of 3,560 feet (with the implementation of <br />the ROM release), would the TEL again become active. <br />=s. <br />